What Is the Purpose of a Firewall?

The primary purpose of a firewall is packet filtering. When a computer sends a request across the Internet, it takes the form of small packets of data, which travel through the network to their destination. The target server responds with its own packets of data, which return along the same route. A firewall monitors every packet that passes through it, considering its source, destination and what type of data it contains, and it compares that information to its internal rule set. If the firewall detects that the packet is unauthorized, it discards the data. Typically, firewalls allow traffic from common programs such email or Web browsers, while discarding most incoming requests. You can also configure a firewall to disallow access to certain websites or services to prevent employees from accessing non-work resources while on the clock.